1. Technical Field
The present invention relates to a projector having a cooling device incorporated therein and capable of cooling a target object such as an optical component on demand.
2. Related Art
There is known a device in, for example, a light path deflection device or a projector having an optical component such as a light path deflection element using a liquid crystal material, having internal temperature sensors for measuring the temperature of the sections the temperature of which the tendency of the temperature of the component can be figured from, and performing control of an air blower for sending air to the optical component in accordance with the temperature measured by each of the temperature sensors in order for maintaining the temperature of the optical component fixedly.
Further, there is known a device having an external temperature sensor for detecting the temperature of the air distributed to the optical component and an internal temperature sensor for detecting the temperature of the place from the temperature of which the tendency of the temperature of the optical component can be estimated, thereby performing control of the air blower for distributing the air to the optical component in accordance with the temperature detected by each of the temperature sensors (JP-A-2004-279924). Further, there is also known a device which detects the temperature condition on the periphery and the inside of the device housing using a plurality of temperature sensors, and performs temperature control, display control, and power supply control in accordance therewith (JP-A-2001-22451). Further, there is known a device which is provided with a section for examining an amount of a load applied to the device in addition to a section for detecting the temperature difference between the internal temperature and the external temperature of the device, thereby making a judgment on blockage of an air charge/discharge port (JP-A-2002-357317).
However, in using the projector, for example, regarding an extent of overheating of the optical component inside the projector, the extent of overheating of the target object such as an optical component inside the projector such as a rate of increase in the temperature thereof cannot necessarily be estimated correctly only by the internal temperature of the projector device because of an influence of, for example, clogging of an air filter for taking the external air in the projector.
FIGS. 4A through 4C are diagrams for explaining the internal temperature condition of the projector which may occur in the projector in the related art by way of exemplification. The projector in the related art is provided with, for example, a thermistor disposed at a predetermined place inside the housing, and performs the temperature control using the temperature (hereinafter referred to as “internal temperature”) measured at that place as a criterion. In this case, as shown in FIG. 4A, in the internal temperature measured at the place where the thermistor is installed and the temperature (hereinafter referred to as “target object temperature”) of what should be the target object of the temperature measurement such as a polarization conversion device, there is the case in which when the room temperature, namely the ambient air temperature is, for example, 25° C., the internal temperature is 45° C., which is 20° C. higher than the room temperature, while the target object temperature is 65° C., which is 40° C. higher than the room temperature. It is conceivable that even in such a case, if the cooling device or the like of the projector operates normally, when, for example, the external environment changes to raise the room temperature to 40° C. as shown in FIG. 4B, the condition in which the internal temperature is 20° C. higher than the room temperature and the target object temperature is 40° C. higher than the room temperature is maintained, and the internal temperature becomes 60° C. while the target object temperature becomes 80° C. However, there is also the case in which the cooling effect is reduced because of, for example, the clogging caused in the air filter attached to the cooling device. In such a case, in comparison between the internal temperature and the target object temperature, the target object temperature, which originally has larger temperature rise, is apt to rise more easily, and consequently, when the cooling effect has reduced, there can be caused the case in which, for example, the internal temperature rises 30° C. to be 55° C. while the room temperature is kept in 25° C., and the target object temperature, which can more easily be raised, becomes 92.5° C. as shown in FIG. 4C. In such a case, as is understood from the comparison between FIGS. 4B and 4C, there is caused the condition in which although the target object temperature to be an important criterion for performing the cooling operation is higher in the condition shown in FIG. 4C, the external temperature and the internal temperature actually measured are both lower in the condition shown in FIG. 4C than in the condition shown in FIG. 4B. In other words, the temperature control performed based on the external room temperature and the internal temperature is not necessarily appropriate.
Therefore, it is desirable to perform measurement with the temperature sensor directly attached to the optical component in the projector. However, the optical component such as a polarization conversion element is usually disposed on the light path in the projector. Therefore, it is not necessarily easy to directly attach the temperature sensor to the optical component for performing measurement because it is required to dispose the temperature sensor at a place where the temperature sensor does not make a shadow on the optical path. Further, there is a possibility of damaging the temperature sensor because of the influence of the heat from the optical component depending on the place where the temperature sensor is attached.
Further, in the case in which the amount of load (e.g., an amount of the power supply current supplied to the entire device) applied to the device in addition to the temperature, it is required to provide the device for measuring the amount of the load separately from the device for measuring the temperature in order for measuring the amount of the load.